[Jewelry making - Article 01055] - Re: [Orchid] Retipping sterling prong

[H.Durstling]

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Hi,

    I've seen similar "splotches" on sapphire after soldering. My
    suspicion is that what's happening is a kind of "vapor deposition"
    with trace amounts of vaporized metal sputtered onto the stone. 

    The set and soldered sapphires were not my own work so I did not
    need to rectify that problem. If it was me that had to, I'd proceed
    on the assumption that the splotches are metal and try two
    approaches, maybe combine both. 

    The first would be to reheat the stone in air to slightly below
    soldering temperature on the assumption that this might oxidize the
    metal; then cool, then coat liberally with flux and re heat, in the
    hope that the flux would dissolve away the oxide formed in the
    previous step. 

    The second would be acid treatment of the stone. Hot nitric (even
    aqua regia if you take the stone out) I believe would be most
    effective, but also dangerous due to fumes; I would do it outdoors on
    a hot plate. I doubt you could do this with the stone in; no matter
    how well you coated the piece with acid-proof resist there is a great
    risk of the acid getting in under the resist to attack the piece.
    Taking the stone out would be safer albeit time consuming. 

    I should emphasise that both these approaches are purely
    theoretical. They are what I would do if confronted with the same
    problem. I have never actually done it. 

    I'd be curious to hear the advice of other Orchideans, and what
    method does finally turn out to work for you. 

Cheers,
Hans Durstling
Moncton,
Canada


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